cutout-birefnet: BiRefNet general (ZhengPeng7/BiRefNet at revision
e2bf8e4460fc8fa32bba5ea4d94b3233d367b0e4), MIT, Copyright (c) 2024 ZhengPeng.
See LICENSE.

Changed for Core AI, in export_birefnet.py:
- torchvision's deform_conv2d is computed from gathers and matrix products
  (identical result: max |alpha difference| 4.6e-6 in float32 on the CPU).
- The ImageNet normalisation and the final sigmoid are inside the graph; only
  the last, full-size prediction is returned.
- Weights and arithmetic are float16; the input and output stay float32.
The trained weights are otherwise the authors', unmodified.